1. Field of the Invention:
The present invention relates to a probe for detecting variations in the composition of a flow of mixed gases and in particular of the exhaust gases of clean-burning internal combustion engines.
2. Description of the Prior Art:
Known probes, called "lambda probes", for detecting variations in the composition of exhaust gases, usually consist of a solid-electrolyte partition, e.g. of zirconium oxide, producing a potential difference between one side which is subjected to the exhaust gases and the other side which is exposed to the atmosphere. These partitions generally have a closed tubular form called "glove-finger", or are flat plates. These types have drawbacks.
For the "glove-finger" probe, the reference zone being a relatively closed volume of air within the "finger", the renewal of this air is poor and there accordingly is a risk of its being polluted by the surrounding exhaust gases, especially if the sealing between the air and exhaust-gas zones is not perfect. The normally occuring expansions and vibrations make this sealing difficult, particularly for the flat plate or lozenge configuration, where the seal must necessarily be exposed to the high-temperature exhaust-gas flow.
These two aspects of existing embodiments thus call for a complicated technology entailing delicate and therefore difficult fabrication, the more so because the severe operating conditions often require their replacement because of rupture or fouling.
The replacement of these probes is made difficult because of this complex technology and their operating environment, leading to oxidation and jamming of the assembled parts.